Fig. 3.

Periaqueductal grey (PAG) response to breath hold. A. Representation of the location of the PAG within the brain, three sagittal slices and the current opinion of the subdivisions of the PAG. B. Localisation of the functional decreases in BOLD signal within the PAG (p < 0.05; small-volume-corrected for multiple comparisons using overlaid PAG mask), where the images consist of a colour-rendered statistical map superimposed on a standard (MNI 1 mm³) brain. Dashed line represents Z-10 location. C. Uncorrected Z score image of PAG deactivation from whole brain analysis, prior to masking. Abbreviations: SN, substantia nigra; RN, red nucleus; SC, superior colliculus; SCP, superior cerebellar peduncle; ICN, inter-colliculi nucleus; IC, inferior colliculus; vl, ventrolateral PAG, l, lateral PAG; dl, dorsolateral PAG; dm, dorsomedial PAG.